James Hagadorn, MD is a neonatologist at the Floating Hospital for Children in Boston, MA, and Assistant Professor of Pediatrics at Tufts University School of Medicine. With the eventual goal of establishing himself as a productive, independent clinical investigator, he intends to study advanced clinical research methods in a formal, structured setting by pursuing a Master of Science in Clinical Care Research at Tufts University's Sackler Graduate School of Biomedical Sciences. The Sackler MS program is supported by a NIH K-30 Clinical Research Curriculum Program Award. The proposed Masters thesis described here will evaluate the hypothesis that cumulative illness severity and frequent fluctuations in clinical status (lability) are important contributors to the progression of retinopathy of prematurity (ROP) in very low birth weight infants. Data for this retrospective study will be collected through review of medical records at three Boston teaching hospitals, and will be used to construct a multivariable predictive model for progression of ROP. An estimated 230 infants of birth weight less than 1251 grams admitted to participating neonatal ICUs between January 1995 and December 2001 had or will develop prethreshold (moderately severe) ROP. Of these, approximately 91 will have progressed to threshold (severe) disease. For each infant in this cohort, the SNAP neonatal illness severity scoring system will be used to quantify the level of illness severity for each day of hospitalization, yielding an objective and dynamic measure of illness severity and the frequency and magnitude of fluctuations in clinical status. The resulting detailed description of the acuity of the infant's hospital course will provide the basis for an unprecedented exploration of the relative contributions of cumulative illness severity and lability to the likelihood of progression to threshold disease in this high-risk group. Interactions between hypothesized predictors of ROP progression will be explored. Identified predictors will be validated on a comparable population of premature infants hospitalized contemporaneously at a fourth academic center in Providence, RI.